I'm trying this code:
private List<book> books;
//private book[] books;
.
.
.
private void button1_Click(object sender, EventArgs e)
{
books.Add(new book(book_name.Text));
//book[0]=new book(book_name.Text);
}
but I'm getting this error:
'Object reference not set to an instance of an object.'
What should I do? I want dynamic creation of object by an event.
You need to initialize your list:
private List<book> books = new List<book>();
You need to instantiate books first, like this:
private List<book> books = new List<book>();
when you say
private List<book> books;
It only creates a reference of type List with null value. So when you try to call the member function of the List structure, it gives an error that the reference is set to null.
You need to initialize the variable using another statement in the constructor
books = new List<book>();
expr.member, whereexprevaluates tonull. In this case that isbooksbecause it was never assigned a value (a new List, perhaps?).